Number of minimal edge covers in the ladder graph P_2 X P_n.

Terms

a(0) =1a(1) =2a(2) =6a(3) =17a(4) =45a(5) =120a(6) =324a(7) =873a(8) =2349a(9) =6322a(10) =17018a(11) =45809a(12) =123305a(13) =331904a(14) =893400a(15) =2404801a(16) =6473097a(17) =17423890a(18) =46900574a(19) =126244129a(20) =339816309a(21) =914696984a(22) =2462126012a(23) =6627401865a(24) =17839239445a(25) =48018585634a(26) =129253524146a(27) =347916817697a(28) =936501444241